@/***************************************************************************
@ * Copyright (c) 2024 Microsoft Corporation 
@ * 
@ * This program and the accompanying materials are made available under the
@ * terms of the MIT License which is available at
@ * https://opensource.org/licenses/MIT.
@ * 
@ * SPDX-License-Identifier: MIT
@ **************************************************************************/
@
@
@/**************************************************************************/
@/**************************************************************************/
@/**                                                                       */ 
@/** ThreadX Component                                                     */ 
@/**                                                                       */
@/**   Thread                                                              */
@/**                                                                       */
@/**************************************************************************/
@/**************************************************************************/
@
@
@#define TX_SOURCE_CODE
@
@
@/* Include necessary system files.  */
@
@#include "tx_api.h"
@#include "tx_thread.h"
@
@
SVC_MODE        =       0x13                    @ SVC mode
#ifdef TX_ENABLE_FIQ_SUPPORT
CPSR_MASK       =       0xDF                    @ Mask initial CPSR, IRQ & FIQ ints enabled
#else
CPSR_MASK       =       0x9F                    @ Mask initial CPSR, IRQ ints enabled
#endif

THUMB_BIT       =       0x20                    @ Thumb-bit

@
@
    .arm
    .text
    .align 2
@/**************************************************************************/ 
@/*                                                                        */ 
@/*  FUNCTION                                               RELEASE        */ 
@/*                                                                        */ 
@/*    _tx_thread_stack_build                          SMP/Cortex-A5/GNU   */
@/*                                                           6.1          */
@/*  AUTHOR                                                                */
@/*                                                                        */
@/*    William E. Lamie, Microsoft Corporation                             */
@/*                                                                        */
@/*  DESCRIPTION                                                           */
@/*                                                                        */ 
@/*    This function builds a stack frame on the supplied thread's stack.  */
@/*    The stack frame results in a fake interrupt return to the supplied  */
@/*    function pointer.                                                   */ 
@/*                                                                        */ 
@/*  INPUT                                                                 */ 
@/*                                                                        */ 
@/*    thread_ptr                            Pointer to thread control blk */
@/*    function_ptr                          Pointer to return function    */
@/*                                                                        */ 
@/*  OUTPUT                                                                */ 
@/*                                                                        */ 
@/*    None                                                                */
@/*                                                                        */ 
@/*  CALLS                                                                 */ 
@/*                                                                        */ 
@/*    None                                                                */
@/*                                                                        */ 
@/*  CALLED BY                                                             */ 
@/*                                                                        */ 
@/*    _tx_thread_create                     Create thread service         */
@/*                                                                        */ 
@/*  RELEASE HISTORY                                                       */ 
@/*                                                                        */ 
@/*    DATE              NAME                      DESCRIPTION             */
@/*                                                                        */
@/*  09-30-2020     William E. Lamie         Initial Version 6.1           */
@/*                                                                        */
@/**************************************************************************/
@VOID   _tx_thread_stack_build(TX_THREAD *thread_ptr, VOID (*function_ptr)(VOID))
@{
    .global _tx_thread_stack_build
    .type _tx_thread_stack_build,function
_tx_thread_stack_build: 
@
@       
@    /* Build a fake interrupt frame.  The form of the fake interrupt stack
@       on the Cortex-A5 should look like the following after it is built:
@       
@       Stack Top:      1           Interrupt stack frame type
@                       CPSR        Initial value for CPSR
@                       a1 (r0)     Initial value for a1
@                       a2 (r1)     Initial value for a2
@                       a3 (r2)     Initial value for a3
@                       a4 (r3)     Initial value for a4
@                       v1 (r4)     Initial value for v1
@                       v2 (r5)     Initial value for v2
@                       v3 (r6)     Initial value for v3
@                       v4 (r7)     Initial value for v4
@                       v5 (r8)     Initial value for v5
@                       sb (r9)     Initial value for sb
@                       sl (r10)    Initial value for sl
@                       fp (r11)    Initial value for fp
@                       ip (r12)    Initial value for ip
@                       lr (r14)    Initial value for lr
@                       pc (r15)    Initial value for pc
@                       0           For stack backtracing
@
@    Stack Bottom: (higher memory address)  */
@
    LDR     r2, [r0, #16]                       @ Pickup end of stack area
    BIC     r2, r2, #7                          @ Ensure 8-byte alignment
    SUB     r2, r2, #76                         @ Allocate space for the stack frame
@
@    /* Actually build the stack frame.  */
@
    MOV     r3, #1                              @ Build interrupt stack type
    STR     r3, [r2, #0]                        @ Store stack type
    MOV     r3, #0                              @ Build initial register value
    STR     r3, [r2, #8]                        @ Store initial r0
    STR     r3, [r2, #12]                       @ Store initial r1
    STR     r3, [r2, #16]                       @ Store initial r2
    STR     r3, [r2, #20]                       @ Store initial r3
    STR     r3, [r2, #24]                       @ Store initial r4
    STR     r3, [r2, #28]                       @ Store initial r5
    STR     r3, [r2, #32]                       @ Store initial r6
    STR     r3, [r2, #36]                       @ Store initial r7
    STR     r3, [r2, #40]                       @ Store initial r8
    STR     r3, [r2, #44]                       @ Store initial r9
    LDR     r3, [r0, #12]                       @ Pickup stack starting address
    STR     r3, [r2, #48]                       @ Store initial r10 (sl)
    MOV     r3, #0                              @ Build initial register value
    STR     r3, [r2, #52]                       @ Store initial r11
    STR     r3, [r2, #56]                       @ Store initial r12
    STR     r3, [r2, #60]                       @ Store initial lr
    STR     r1, [r2, #64]                       @ Store initial pc
    STR     r3, [r2, #68]                       @ 0 for back-trace

    MRS     r3, CPSR                            @ Pickup CPSR
    BIC     r3, r3, #CPSR_MASK                  @ Mask mode bits of CPSR
    ORR     r3, r3, #SVC_MODE                   @ Build CPSR, SVC mode, interrupts enabled
    BIC     r3, r3, #THUMB_BIT                  @ Clear Thumb-bit by default
    AND     r1, r1, #1                          @ Determine if the entry function is in Thumb mode
    CMP     r1, #1                              @ Is the Thumb-bit set?
    ORREQ   r3, r3, #THUMB_BIT                  @ Yes, set the Thumb-bit
    STR     r3, [r2, #4]                        @ Store initial CPSR
@
@    /* Setup stack pointer.  */
@    thread_ptr -> tx_thread_stack_ptr =  r2;
@
    STR     r2, [r0, #8]                        @ Save stack pointer in thread's
                                                @   control block

@
@    /* Set ready bit in thread control block.  */
@
    LDR     r2, [r0, #152]                      @ Pickup word with ready bit
    ORR     r2, r2, #0x8000                     @ Build ready bit set
    STR     r2, [r0, #152]                      @ Set ready bit

#ifdef __THUMB_INTERWORK
    BX      lr                                  @ Return to caller
#else
    MOV     pc, lr                              @ Return to caller
#endif
@}

